Identify hyenas

Every hyena has a unique spot pattern. Individual hyenas additionally differ in their fur style and colour. While some have short, blond fur with large dark spots, others have fluffy, reddish fur with fuzzy spots. Because an individual’s spot pattern does not change with age, these characteristics allow us to distinguish spotted hyenas from each other and identify them individually.

The colour and length of the fur do vary with age. This influences how easily an individual can be identified. Spotted hyenas are born with a black fur. At the age of about 1 month, the fur brightens and the spots appear, starting on the shoulders and front legs. By the age of 4 months, all spots usually have emerged. At about 7 to 15 months of age, the hairs grow longer, blurring the spot pattern and making identification a true challenge even for experienced observers. After this period, the hairs grow shorter again and the pattern reemerges. When hyenas grow very old, they may lose hairs and the hairs grow very short causing the spots to fade but the pattern usually remains recognisable.

After spending some time monitoring spotted hyenas, one gets to memorise the spot patterns of various hyenas, but knowing by heart all patterns of a population of up to 550 hyenas is difficult. And it does not help that the patterns of the two body sides of an individual differ from each other…

We use ‘ID cards’ that we compile for each hyena. These ID cards consist of printed photographs of both body sides of an individual and information such as the ID number, name and date of birth. The ID cards are sorted by clans to more quickly find a match when encountering a hyena in the territory of a given clan (but mind the intruders!).

Hyenas usually are identified by directly comparing the photograph on the ID card with the real pattern but when pressed for time, we take new photographs and compare the patterns later on. In this respect, digital cameras have proven to be an extremely helpful and important piece of equipment for our work.

But what if the fur gets dirty? After all, hyenas are quite fond of taking baths in muddy puddles and ponds, especially on hot days. Trying to distinguish the real spots from mud marks may then be real headache. Luckily, spotted hyenas have other attributes that we can use as identification cues such as ear notches and scars. And if one gets to spend a lot of time with them, they can also be recognised by their body shape, personality traits, and their way of walking.

Habituate and observe hyenas

Since the Ngorongoro Crater is replete with potentially dangerous wild animals, all our work is done by car. To be able to approach hyenas with a car and observe their natural behaviour, they need to be habituated to the presence of the car.

Spotted hyenas are generally shy and cautious when approached by humans and vehicles – like most free-ranging animals. But they are also quite curious and can be habituated relatively easily if they are given enough time. This works best when they are very young. Once they gained confidence and trust the observers, young hyenas are very curious. And when they grow older, they hardly pay attention to the observers in their vehicles.

Every hyena has its own character and undergoes different experiences. They behave differently towards conspecifics, competitors, prey and human beings. Hyenas thus also vary in their degree of habituation. For example, most members of the Triangle Clan are more careful than members of other clans because they regularly encounter vehicles and people chasing them during their visits to the Crater rim.

To monitor the natural behaviour of a hyena, it is crucial to acknowledge its personality and only approach as close as it accepts it. To assess the minimum distance tolerated by a hyena one simply has to pay attention to its behaviour – if the hyena becomes anxious or retreats, it indicates that one came too close and the respectful way to react is to retreat.

Determine the sex of hyenas

Young females and males are hard to distinguish from each other by external examination. First, females have an elongated clitoris or ‘pseudopenis’ that can be erected and that closely resembles a male penis. Second, their outer labia are fused and filled with tissue and closely resemble and are located at the same position as the scrotum of hyena males. Third, young females have very small teats that are barely visible, and contrary to common belief, there are no significant differences in body size and build between females and males.

It is therefore not very surprising that zoos regularly get confused, and report ‘male’ hyenas giving birth to cubs or that they suddenly discover, that an ‘infertile couple’ actually consisted of two females or two males.

The best way to sex a spotted hyena is to take a close look at the tip of the penis or ‘pseudopenis’ when it is erected: the penis of male spotted hyenas has a pointed tip and a clearly visible narrowing immediately above the glans whereas the female ‘pseudopenis’ has a rounded tip and lacks a narrowing. The best chance to see these characteristics is when two hyenas meet each other and perform the ritualised greeting ceremony.

Determine the social rank of hyenas

Social interactions are essential to assess the dominance relationship between hyenas. To determine the hierarchy within an entire hyena clan every hyena has to be observed interacting with all other clan members. The dominance relationships between the two individuals are then established based on their behaviour and body postures. The dominant individual has its tail upright and ears cocked whereas the subordinate individual keeps its tail between the legs, has the ears backwards, the teeth bared, and the head downwards.

The ritualised greeting ceremonies are particularly useful to get an idea of the dominance relationship between individuals. When two hyenas meet, the subordinate animal erects its penis or ‘pseudopenis’ and is the first to lift its hind leg or lies down first to let the dominant animal examine its anogenital region. These rituals confirm the dominance relationships and strengthen friendships and coalitions. Hyenas initiate such greeting ceremonies from very early on (as early as four weeks old) and thereby learn which clan members are lower-ranking and which are higher-ranking.

Find the genetic father and mother

Knowing both parents of a cub is crucial. A key element of our research is to determine the reproductive success of our males and females and the establishment of a detailed pedigree. To do this, we need to assign a mother and a father to each cub. Because fathers do not provide care to their offspring and females (in rare cases) may adopt cubs from another female, we cannot rely on behavioural observations only and have to perform genetic parentage analyses.

We extract DNA from faeces, hair and tissue samples that we collect using non-invasive methods. Hyena faeces are covered with a thin layer of mucus that contains intestinal epithelium cells. This layer can be easily collected and stored in a small tube with a preservative solution. Faeces are collected immediately after defecation to ensure assignment to the correct individual. Hairs are collected when curious cubs approach the vehicle, and tissue when animals are found dead.

The genetic analyses are conducted in Berlin. The first step in our lab is to extract DNA from the cells of the intestinal epithelium, hair roots and tissue using standard commercially available kits. In a second step, gene fragments of nine different areas or ‘loci’ of the hyena genome are multiplied using Polymerase Chain Reaction (PCR). These fragments or ‘microsatellites’ vary in their length and each length corresponds to an ‘allele’; our loci have up to 16 different alleles. In the third step of the analysis, the lengths of the fragments are measured and assigned to the alleles. Each individual has two alleles per locus, one that it inherited from the mother and one that originates from the father. Thus, to find out who the genetic mother and father of an individual is, we then simply have to compare the combination of alleles of the nine loci of the individual with that of the candidate mothers and fathers.